Radiosurgery and radiotherapy systems are radiation treatment systems that use external radiation beams to treat pathological anatomies (e.g., tumors, lesions, vascular malformations, nerve disorders, etc.) by delivering a prescribed dose of radiation (e.g., x-rays) to the pathological anatomy while minimizing radiation exposure to surrounding tissue and critical anatomical structures (e.g., the spinal cord). Both radiosurgery and radiotherapy are designed to necrotize the pathological anatomy while sparing healthy tissue and the critical structures. Radiotherapy is characterized by a low radiation dose per treatment, and many treatments (e.g., 30 to 45 days of treatment). Radiosurgery is characterized by a relatively high radiation dose in one, or at most a few, treatments.
In both radiotherapy and radiosurgery, the radiation dose is delivered to the site of the pathological anatomy from multiple angles. As the angle of each radiation beam is different, each beam can intersect a target region occupied by the pathological anatomy, while passing through different regions of healthy tissue on its way to and from the target region. As a result, the cumulative radiation dose in the target region is high and the average radiation dose to healthy tissue and critical structures is low. Radiotherapy and radiosurgery treatment systems can be classified as frame-based or image-guided.
One challenge facing the delivery of radiation to treat pathological anatomies, such as tumors or lesions, is identifying the location of the target (i.e. tumor location within a patient). The most common technique currently used to identify and target a tumor location for treatment involves a diagnostic x-ray or fluoroscopy system to image the patient's body to detect the position of the tumor. This technique assumes that the tumor does not move appreciably over the course of a treatment.
Current methods track and account for tumor motion during delivery of radiation treatment using multiple diagnostic x-rays over the course of treatment, as the skilled artisan will appreciate. In these current methods and systems a user specifies how many radiation treatment beams should be delivered between each diagnostic x-ray image. In such systems, delivery of beams can vary drastically in time duration. For example, imaging every 3 beams could result in one pair of images taken 10 seconds apart, interleaved by 3 short beams, followed by an image taken more than a minute later after 3 long beams. However, the tumor may have moved between the two diagnostic x-ray images, thereby resulting in less than desired accuracy of delivery of treatment radiation beams to the target, and a larger than desired radiation dose delivered to healthy tissue surrounding the target.